The conductivity and magnetoresistance of La0.5Pb0.5Mn1−xCrxO3 (0.0⩽x⩽0.45) measured at 0.0 1.5 T magnetic field have been reported. All the oxide samples except x=0.45, showed metal insulator transition (MIT) between 158–276 K, depending on x. In contrast to behavior a similar sample La0.7Ca0.3Mn1−xCrxO3 showing no for x⩾0.3, Pb doped MIT even with x=0.35. peak temperature (Tp) shifts towards lower increasing x while Tp high regime. metallic (ferromagnetic) part dependent resistivity (ρ)...

Exchange-bias (EB) phenomena have been observed in the ${L}_{0.5}{\mathrm{Sr}}_{0.5}\mathrm{Mn}{\mathrm{O}}_{3}$ ($L=\mathrm{Y}$, ${\mathrm{Y}}_{0.5}{\mathrm{Sm}}_{0.5}$, and ${\mathrm{Y}}_{0.5}{\mathrm{La}}_{0.5}$)-type manganites showing cluster-glass-like spin-glass-like behavior. The field cooled magnetic hysteresis loops exhibit shifts both magnetization axes. values of exchange $({H}_{E})$, coercivity $({H}_{C})$, remanence asymmetry $({M}_{E})$, $({M}_{C})$ are found to depend...

Bulk copper (II) oxide (CuO), heat treated at 1223K, shows extraordinarily high dielectric constant (εr∼104), almost independent of temperature (above 230K) and frequency in the kilohertz region. A sudden decrease εr is observed lower (below 150K). X-ray photoelectron spectroscopy resolution transmission electron microscopy studies confirm presence a microscopic amount Cu3+ annealed CuO. The behavior CuO can be explained by Maxwell-Wagner-type polarization mechanism thermally activated mechanism.

Semiconducting oxides such as Bi4Sr3Ca3CuyOx (y=0–5) and Bi4Sr3Ca3−zLizCu4Ox (z=0.1, 0.5, 1.0), many of which become superconductors in their glass-ceramic phases, have been studied over the wide temperature (77–450 K) frequency (100–104 Hz) ranges. The universal power-law behavior [exponent s≤1 σ(ω)=σ0+Aωs] is found to be valid for most these glasses. Little deviation from this limiting also observed some glass compositions low-temperature high-frequency regions. correlated barrier hopping...

Dielectric spectroscopy analysis of the high permittivity (κ∼104) copper (II) oxide (CuO) ceramic shows that grain contribution plays a major role for giant-κ value at low temperature, whereas boundary (GB) dominates around room temperature and above. Moreover, impedance reveals electrically heterogeneous microstructure in CuO consisting semiconducting grains insulating GBs. Finally, giant dielectric phenomenon exhibited by is attributed to internal barrier layer (due GB) capacitance mechanism.

Two different phases of LaMnO3+δ [one showing a metal–insulator transition (MIT), referred to as LaMn–C, and the other not MIT, LaMn-S] have been clearly observed follow two conduction mechanisms. Interestingly, small polaron hopping models Mott, Schnakenberg, Emin are found fit conductivity data all samples above corresponding MIT temperature. The insulating (semiconducting) LaMn–S followed nonadiabatic mechanism while LaMn–C Pb doped viz. La1−xPbxMnO3 (x=0.05–0.5) showed similar type an...

The effect of particle size on the transport properties (resistivity and thermopower) La0.5Pb0.5MnO3 has been investigated both in presence absence magnetic field B=0.0–1.5 T (maximum). Grain size, dc conductivity; metal–insulator transition temperature Tp sample increase with increasing annealing time. has, however, comparatively little Seebeck coefficient S. Magnetoresistance is higher for samples smaller grain sizes. susceptibility also increases size. High (T>θD/2) resistivity...

From the low-temperature (down to 10K) dc-magnetization data of La0.7Sr0.3MnO3 (LSM), La0.7Ca0.3MnO3 (LCM), and Pr0.7Ca0.3MnO3 (PCM) systems, we estimated critical exponents β, γ, hence δ from analysis modified Arrot plots. The exponent β for LCM system is less than that predicted by Heisenberg model resides within zone Ising while LSM sample, higher which considered be due presence dipole-dipole interaction arising large spin moment in system. magnetization PCM cannot fitted plots, suggest...

We report a diffuse phase transition (extending over finite temperature range of ∼50 K) in sol-gel derived nanoparticles (∼25 nm) the ferromagnetic double perovskite La(2)NiMnO(6). The macroscopic polarization (P-E hysteresis loop), validity Vogel-Fulcher relation and high dielectric permittivity (∼9 × 10(2)) confirm relaxor ferroelectric phenomena these magnetic nanoparticles. Compared to corresponding bulk sample, appreciably large enhancement magnetocapacitive effect (MC ∼ 30%) is...

Abstract A novel two‐phase polymer nanocomposite film comprising of polyvinylidene fluoride (PVDF) and nanocrystalline (∼90 nm) semiconducting multiferroic BiFeO 3 (BFO) have been fabricated by hot‐molding technique. Such flexible thick films, semicrystalline in nature, exhibited extraordinarily high effective dielectric permittivity ε eff ∼ 10 (compared with that pure PVDF) near the low percolation threshold ( f c = 0.12) at room temperature (RT) films also possessed loss (∼0.18). The...

We report the results of thermoelectric power (TEP) a Cr doped ${\mathrm{La}}_{0.5}{\mathrm{Pb}}_{0.5}{\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}{\mathrm{O}}_{3}$ $(x=0--0.45)$ system measured both in presence and absence magnetic field $(B=1.5\mathrm{T}).$ The small dependence Seebeck coefficient is observed around metal-semiconductor transition (MST) temperature ${(T}_{p})$ samples. TEP stronger undoped sample. It noticed from data that polaron hopping conduction mechanism valid for...

With increasing the Li doping level in La0.7Ca0.3−yLiyMnO3 (0⩽y⩽0.3), system is driven from a higher-conductivity regime to lower-conductivity regime, which sharp contrast with behavior of Na or K doping. Compared those Na, ionic radius much smaller than that Ca. Therefore, substitution Ca by results average A-site radius, narrowing bandwidth and hence enhancing band gap resistivity. The effect random disorder La3+ A2+ also plays an important role leading charge localization.

KxTiyNi1−x−yO(x = 0.05–0.3, y 0.02–0.25) ceramics (abbreviated as KTNO) have been synthesized showing high permittivity. All the KTNO samples of varying compositions exhibit dielectric permittivity (∼104) near room temperature, which is comparable to that recently discovered CaCu3Ti4O12 (CCTO) ceramic. The constant depends on both K and Ti content can be attributed Maxwell–Wagner polarization mechanism a thermally activated mechanism.

Homogeneous thick film (∼0.10 mm) of high dielectric K0.05Ti0.02Ni0.93O; abbreviated as KTNO/polyvinylidene fluoride (PVDF) composite has been prepared by hot-molding technique. The frequency and temperature dependent behavior this studied varying the KTNO volume fraction (fKTNO). Near percolation threshold (fKTNO=0.40), a large enhancement effective permittivity (εeff∼400 which is 40 times higher than that pure PVDF) with low loss (∼0.20 at 1 kHz) observed. experimental εeff data have...

Abstract Graphite oxide nanoplatelets (GOnP) were prepared using standard method and used to make GOnP‐polyvinyl alcohol (PVA) composites by solution cast technique. Significant enhancement of electrical conductivity dielectric permittivity the GOnP/PVA are observed at low GOnP concentration ( f = c ∼0.41 vol%) which is percolation threshold value estimated from dependent transport data. Nearly 300 times increase in (compared with that PVA) composite around . We notice interesting...

The frequency dependent ultrasonic velocities (both longitudinal and shear) attenuation in BaTiO3 doped (80V2O5–20PbO + xBaTiO3) oxide (VPB) glasses (for x = 0, 1, 5, 10, 15 wt% of the base glass) have been measured using pulse echo overlap method at room temperature. From velocity, density attenuation, various parameters namely longitudinal, shear, bulk, Young's moduli, Debye temperature, Poisson's ratio, acoustic impedance microhardness VPB were determined. All these increase with addition...

Ternary vanadium oxide glasses in the system ${\mathrm{V}}_{2}{\mathrm{O}}_{5}{\ensuremath{-}\mathrm{C}\mathrm{o}\mathrm{O}\ensuremath{-}\mathrm{T}\mathrm{e}\mathrm{O}}_{2}$ are fabricated by press quenching of glass melts, and dc conductivities (\ensuremath{\sigma}) investigated at temperatures from 330 to 475 K for different compositions. From study phase diagram, formation region is found be range ${\mathrm{V}}_{2}{\mathrm{O}}_{5}=0--85\mathrm{mol}%,$ $\mathrm{CoO}=0--35\mathrm{mol}%,$...

Abstract Flexible magnetoelectric 0–3 composite films formed with high dielectric ( ε r ∼ 10 4 ) CuO microparticles in a polyvinylidene fluoride (PVDF) polymer matrix showed multifunctional properties. The prepared by the hot-moulding technique exhibit low-loss relative permittivity eff 3 good ferroelectric behaviour (with P – E loop) at percolation threshold f = c 0.25). Dielectric, ferroelectric, magnetic and direct properties of composites depend strongly on filler concentration )....

Above the semiconductor-to-metallic transition (SMT) temperature (Tp), transport properties of La1−xPbxMnO3+δ (0 ≤ x 0.5)-type mixed valence oxides with Tp between 230 and 275 K (depending on x) have been thoroughly examined for a small-polaron hopping conduction mechanism carriers. Although variable range (VRH) model was used earlier to fit entire conductivity data above SMT, we noticed two distinct regions (above below θD/2; θD is Debye temperature) where different types mechanisms are...